Carbamate derivatives are useful in a variety of applications, including, but not limited to, uses in pesticides, insecticides, antibiotics, and in the synthesis of polyurethanes. Polyurethanes prepared from carbamate derivatives, particularly, hydroxyalkylcarbamates, are useful in a variety of applications, including various coating technologies, as further discussed in Low VOC Carbamate Functional Coatings Compositions for Automotive Topcoats, Marvin L. Green, presented at the International Waterborne, High-Solids, and Powder Coating Symposium, Mar. 1-3, 2000, New Orleans, La., which is incorporated by reference.
Of particular interest in automotive clear coat technology, is the utilization of recently commercialized hydroxypropylcarbamate (HPC) compounds, which are typically prepared from five-membered carbonate rings. Unfortunately, the purification of such HPC compounds is complicated by the competing reverse reaction. Specifically, upon purification (i.e. removal of excess ammonia), such HPC compounds tend to revert back to their starting materials. As such, these HPC compounds tend to become easily contaminated if not handled properly.
Unlike carbamates produced from five-membered cyclic carbonates, carbamates produced from six-membered cyclic carbonates are easier to purify. In particular, upon purification (i.e.removal of excess ammonia), carbamates prepared from six-membered cyclic carbonates do not revert back to their starting materials. Presumably, this stability is due to the increased ring strain of six-membered cyclic carbonates, as compared with their five-membered counterparts. As such, hydroxyalkylcarbamates prepared from six-membered cyclic carbonates have superior handling characteristics, over hydroxyalkylcarbamates prepared from five-membered cyclic carbonates.